Halogen Bonding in the Assembly of Coordination Polymers Based on 5-Iodo-Isophthalic Acid

series of seven divalent coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and ancillary nitrogen ligands (phen = 1,10-phenanthroline, bpe = 1,2-bis(4-pyridyl)ethene, p-bix = 1,4-bis (imidazol-1-ylmethyl)-benzene, m-bix = 1,3-bis(imidazol-1-ylmethyl)-benzene), namely, [Zn-2(5-iipa)(2)(phen)(2)(H2O)](n) (1), [Zn(5-iipa)(bpe)(1.5)](n) (2), [Cd-2(5-iipa)(2)(phen)(2)](n) (3), [Mn-2(5-iipa)(2)(phen)(2)](n) (4), [Mn-4(5-iipa)(4)(bpe)(4)center dot 5H(2)O] (5), [Co(5-iipa)(p-bix)](n) (6), and [Co(5-iipa)(m-bix)](n) (7), have been synthesized. The structure of compound 1 exhibits a double zigzag metal-organic chain, and such chains are further united together to generate a three-dimensional (3D) supramolecular structure through interchain I center dot center dot center dot pi interactions. Compound 2 features interesting 3-fold parallel interpenetrated two-dimensional (2D) -> 3D network motifs which are stabilized by interlayer I center dot center dot center dot pi, pi center dot center dot center dot pi, and C-H center dot center dot center dot pi interactions. In isomorphous compounds 3 and 4, the 5-iipa(2-) ligand acts as mu(3)-bridge to connect metal atoms to form a 2D metal-organic layer, and such layers are united together to yield a 3D supramolecular structure through interlayer I center dot center dot center dot pi and C-H center dot center dot center dot pi interactions. In the structures of 5 and 7, the rare 2-fold interpenetrating 3D supramolecular architectures based on I center dot center dot center dot I interactions or O center dot center dot center dot I halogen bonding are found, respectively. In compound 6, 3-fold interpenetrated 2D -> 3D network motifs based on covalent bonding are expanded to a rare 3D supramolecular structure based on O center dot center dot center dot I halogen bonding. 'The above results demonstrate a useful guideline in the crystal engineering of supramolecular architectures in coordination network assembly under the influence of halogen bonding as well as related I center dot center dot center dot I and I center dot center dot center dot pi interactions. Their thermal analysis, X-ray diffraction, UV-vis absorption spectra, and photoluminescent properties have been investigated as well.